1. Field of the Invention
The present invention relates to a method in accordance with the preamble of claim 1 for the determination of end head size and location.
2. Description of Related Art
A wide paper roll from the pap machine is transferred to the slitter and slit into rolls of desired width. Next, the rolls are wrapped in the roll wrapper for transportation. In the roll wrapper the roll diameter and width is measured, and on the basis of the measurement results, the width and length of required wrap as well as the diameters of end heads are determined. Wrapping is started by first wrapping the wrap around the roll. The wrap is wider than the roll, allowing the wrap rims to extend over the roll edges. After the wrapping of the wrap around the roll, the inside end heads are inserted to the ends of the paper roll. The inside heads are held in position and the wrap rims are simultaneously crimped over the roll edges. Finally, the outside heads are inserted to the ends of the roll, over the crimped rims of the wrap.
The roll wrappers are automated and the end heads are fetched from the end head stacks by means of suction cup arms. In order to correctly place the heads on the ends of the roll, the stack of end heads must be located in an exactly predetermined place. Conventional end heading stations are provided with a storage rack of end heads having several rotatable shelves. Each shelf contains heads of a different size, and the heads are exactly located on the shelves by means of guides. The machine's control system is provided with information on the size of each head type on any shelf and on the coordinates of the center point of heads in each stack. When the gauging system of the roll wrapper has measured the roll's diameter, it indicates the shelf from which the proper end head is to be fetched, whereby the shelf containing heads of proper size is rotated out from the storage rack of end heads. The suction cup arm then picks up the head at its center and inserts a head onto the roll's end.
The method described above does not provide for the positional measurement of the suction cup arm at the head's center nor for the gauging of the head diameter. Consequently, the method has several disadvantages Because of the lacking positional measurement of the heads' actual location, the stacks of heads must be exactly preplaced to their correct locations, thus necessitating a relatively low height of the head stacks and additionally the use of guides for bracing the stacks. The low-height stacks must be restocked at frequent intervals, which increases the workload of personnel operating the roll wrapper. Furthermore, the system has a low level of controllability and flexibility, since the control system must be provided with prior information on the locations of different size heads and which sizes of heads are available. The system is incapable of detecting incorrect picking of the head or loss of the head prior to its insertion to the end of the roll. Therefore, the machine operation must be continually supervised, and, the machine is incapable of performing a corrective action automatically. Instead the machine requires stopping and guidance back to the step preceding the fault.